Set a field in a hash stored at key with an optional expiration time. Args: name: The Redis hash key. key: The field name inside the hash. value: The value to set. expire_seconds: Optional; time in seconds after which the key should expire. Returns: A success message or an error message.
AI agents use hset to create or update resources in Redis MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Redis MCP Server environment.
The hset tool creates or modifies data (a hash field in Redis) reversibly. This is a classic Write operation—it can be undone by updating the value again or deleting the key. It does not execute arbitrary code (Execute), permanently destroy data (Destructive), or involve financial transactions (Financial).
From the tool's definition Tool description states 'Set a field in a hash' and accepts parameters for name, key, value, and optional expiration. The action of setting a value is a write operation that modifies data in Redis.
Documented attack patterns abuse exactly the kind of access hset gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Redis MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for hset:
{
"version": "1",
"default": "deny",
"tools": {
"hset": {
"limits": [
{
"counter": "hset_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}hset stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Set a field in a hash stored at key with an optional expiration time. Args: name: The Redis hash key. key: The field name inside the hash. value: The value to set. expire_seconds: Optional; time in seconds after which the key should expire. Returns: A success message or an error message. It is categorised as a Write tool in the Redis MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Redis MCP Server MCP server in PolicyLayer and add a rule for hset: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Redis MCP Server. Nothing to install.
hset is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the hset rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for hset. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
hset is provided by the Redis MCP Server MCP server (redis/mcp-redis). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 53 Redis MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
53 Redis MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.